DESCRIPTION(provided by applicant): This proposal requests funds to purchase an R-AXIS IV++ imaging plate X-ray detector for the structural biologists in the Departments of Chemistry and Molecular, Cellular and Developmental Biology at the University of California, Santa Cruz. The current detector (R-AXIS IIC) has been nonfunctional for over 10 months and repeated efforts to locate the cause of the malfunction both by members of the structural biology group at UCSC as well as the manufacturers have been unsuccessful. There are currently three crystallography laboratories at UCSC pursuing a diverse range of exciting research projects. The projects under investigation include (1). the 70S ribosome, complexes with mRNA and tRNA, complexes of the ribosome with trigger factor, ribosome recycling factor and release factors, (2) complexes of the hammerhead ribozyme with transition state analogues, (3) the hairpin ribozyme, (4) RNaseP, (5) flavoenzymes, and (6) multifunctional enzymes involved in substrate channeling. The projects range from those for which crystals are already available to those where crystallization screening is underway to either improve current crystals or to identify new crystallization conditions. For all projects under study, progress is seriously hampered by the fact that there is no functioning in-house X-ray detector currently available. We propose to purchase the R-AXIS IV++ imaging plate detector and a number of accessory items including a 2 theta stage and confocal optical system in order to have a state-of-the-art system that can be used for routine screening of crystals as well as high-resolution data collection.